Why are some people early birds and others are night owls?

Why are some people up with the birds and others hate the mornings? Genetics plays a big role.
Why are some people up with the birds and others hate the mornings? Genetics plays a big role.
Iakov Kalinin/Hemera/Thinkstock

As I write this, my part-time workday is just beginning, yet my husband is tucked into bed, dreaming sweet dreams about tennis matches and Corvettes and other stuff he loves ... at 9:29 p.m. He is your quintessential early bird, and although I don't quite qualify as a night owl, I definitely prefer to turn in a little later in the evening than he does, and certainly rise later than his standard 5:30 a.m.

It turns out that my hubby is a relative rarity, as only about one in ten people qualify as true early birds, or larks (hitting the hay around 9 p.m.), while two in ten classify as owls, burning the midnight-or-later oil on a consistent basis. The rest of us (myself included) fall somewhere in the middle, often referred to as hummingbirds, and are comfortable switch-hitting as needed for social or work-related purposes, though we may have owlish or larkish tendencies [sources: Smolensky and Lamberg, Breus]. It's pretty easy to spot true morning people because they consistently start their days early, even on the weekends, whereas night people who are forced to function on a normal weekday schedule relish a good sleep-in.

Although I've always been of the opinion that this behavior is learned, science is doing its darndest to prove me wrong. In fact, research seems to point squarely at genetics as the culprit for whether someone wakes up bright-eyed and bushy-tailed or not. "Recent discoveries suggest that there are 'clock genes' that run human circadian rhythms," explains Michael Breus, Ph.D, DABSM, author of Secrets to Sleep Success.

Specifically, changes to a gene known as PER1 can affect early bird/night owl status, as it's a component of a larger group of genes known to impact circadian rhythms. Apparently, even minor variations to PER1 can affect your body's natural rise-and-shine time, and it appears that our bodies are primed pretty much from birth to have specific preferences [source: Borreli]. This genetic wild card probably explains why some of us have longer circadian rhythms, resulting in night owl status, as opposed to morning people with shorter internal clocks [source: Oakley].

Next, let's take a look at some of the bizarre ways these sleep preferences affect our personalities, success and even — gulp — time of death.